A liquid crystal display is provided with a thin film transistor (TFT) on a substrate, and the TFT is one of key parts of the liquid crystal display and has great influence on the operation performance of a display device. Each pixel unit in the liquid crystal display is driven by the TFT provided therein, and then high-speed, high-brightness and high-contrast display can be achieved.
Recently, low-resistance copper film starts to be used as an electrode of the TFT and a wiring in a semiconductor integrated circuit, the liquid crystal display and etc., and due to the low resistance of copper, the transmission speed of digital signal can be improved and power consumption can be lowered. However, the adhesion between the copper film and a semiconductor active layer in the TFT is poor, and additionally, a copper atom in the copper film may diffuse to the semiconductor active layer contacting it, this affects the characteristics of the semiconductor active layer. In addition, the adhesion between the copper film and a base substrate and an insulating layer is also poor, during actual use, the copper fill will easily fall off, and then the service life of the product is shortened.
Therefore, the reliability of the TFT will be lowered when the low-resistance copper film is used to make the electrode of the TFT.